(a) Field of the Invention
This invention relates to resin intake manifolds such as provided in intake systems of motor vehicle engines.
(b) Description of the Related Art
Surge tank-integrated intake manifolds are conventionally known as resin intake manifolds of the above kind (see, for example, Published Japanese Patent Application No. H09-177624). The surge tank-integrated intake manifold disclosed in the patent document is formed by integrating a plurality of intake pipes forming intake passages each for supplying intake air to associated one of cylinders of a multi-cylinder engine with a surge tank connected to the upstream sides of the intake pipes. The intake pipes are internally provided with individual internal pipes formed to extend to the interior of the surge tank. The provision of the internal pipes allows the intake passages in the intake pipes to be extended to the interior of the surge tank, thereby enhancing the air intake performance and the silencing effect.
The manifold body of the intake manifold is composed of two split components split along a radial direction of the intake pipes. Each split component is provided with concave parts each of which forms a half of the inner periphery of the associated intake pipe. Each internal pipe is configured to be placed between an opposed pair of concave parts of both the split components. With the internal pipes put between their associated opposed pairs of concave parts, both the split components are joined together by vibration welding. Thus, the internal pipes are held radially gripped between their associated pairs of concave parts of the split components.
Since the internal pipes must be placed in the associated intake pipes as described above, it is necessary that in producing the intake manifold, the outer peripheries of the internal pipes should be fitted onto their associated concave parts of one of the split components to combine the internal pipes with the one split component and, in this state, the other split component should be vibrated with respect to the one split component to weld them together. In this case, in order to provide a firm and reliable vibration welding, a clearance corresponding to the amplitude of vibrations during vibration welding must be kept between each concave part of the other split component and the outer periphery of the associated internal pipe to make the other split component easy to vibrate. If the clearance is kept, part of intake air in the surge tank may flow into the clearance, bypass the internal pipe and then directly reach the downstream side of the intake pipe. This reduces effects due to provision of the internal pipes, such as enhancement in air intake performance and silencing effect.
The present invention has been made in view of the foregoing points and, therefore, an object of the present invention is that when one or more internal pipes are placed in a manifold body which is to be obtained by joining a plurality of split components by vibration welding, a firm and reliable vibration welding can be implemented and, concurrently, intake air in the surge tank can be prevented from bypassing the internal pipes and flowing directly downstream thereof, thereby providing a sufficient effect of enhancing the air intake performance and a sufficient silencing effect both due to provision of the internal pipes.